In photovoltaics, for many years there have already been approaches for working with concentrated solar radiation. In this case, the radiation from the sun is concentrated by means of mirrors and/or lenses, and directed onto specific concentrator solar cells. Corresponding systems of concentrating photovoltaics (CPV) are currently being tested in the Spanish Solar Research Institute (Instituto de Sistemas Fotovoltaicos de Concentracion (ISFOC)) in Castile at Puertollano. They concentrate the sunlight using lenses or mirrors to four hundred- to thousand-fold intensity before it impinges on small solar cells, which are significantly more efficient than traditional silicon solar cells. Manufacturers from many parts of the world have installed CPV modules on the test site there. Approximately a thousand modules are currently installed on the site. Researchers are developing return prognoses, inter alia, and testing long-term stability in order to facilitate the transition from development to the markets for this technology.
Globally only a small number of CPV installations have been in operation hitherto. Their total power of approximately 30 megawatts corresponds approximately to the power of three nuclear power stations. A recent study by the American Market Research Institute Greentechmedia Research predicts, however, that this technology will advance apace. Accordingly, the CPV power installed annually might be 1000 megawatts as early as in 2015. Under favorable conditions, one kilowatt-hour of electrical energy from CPV installations, according to a study by the Fraunhofer Institute for solar energy systems (ISE) in Freiburg, costs between 18 and 21 cents per kilowatt-hour. Further cost reductions through more efficient components and mature industrial production are firmly expected.
At the heart of the installations are the high-power solar cells, which at present are in use primarily in space, where for years they have already been supplying satellites and robots with power. Instead of silicon, these cells contain so-called compound semiconductors composed of gallium, indium, arsenic or phosphorus. They consist of a plurality of different semiconductor layers, each of which processes a different range of the sunlight spectrum, while traditional silicon cells can convert only a smaller portion of the sunlight spectrum into electrical power. The following prior art is cited from the patent literature.
U.S. Pat. No. 4,834,805 discloses a photovoltaic power module comprising the following features.
An arrangement of photovoltaic semiconductor crystal cells, distributed in individual cell locations in a layered substrate, wherein they are enclosed by two electrically conductive layers and separated by means of an insulating layer. Furthermore, this module consists of a light-conveying layer composed of lenses, which is arranged at a distance from the layered substrate, wherein incident radiation is focused into the substrate in the light-conveying layer by means of the lens, and wherein the thickness of the lens layer, of the substrate layer and of the space therebetween is less than 2 inches.
DE 10 2006 007 472 A1 discloses a photovoltaic concentrator module comprising a lens plate and a baseplate, on which solar cells are accommodated, and a frame, wherein the frame, connecting the lens plate and the baseplate, is arranged circumferentially along the edge of the lens plate and the baseplate.
This known concentrator module is intended to be improved to the effect that it can be produced cost-effectively, has a long service life, and that it allows simple and flexible integration of additional components that cannot be accommodated, or can be accommodated only with difficulty, on the lens plate or the baseplate. Furthermore, the intention is to develop a method that makes it possible to produce such concentrator modules.
The problem stated here is solved by virtue of the fact that along the frame between the lens plate and the frame and/or the baseplate and the frame, first, at least one first sealing compound and/or adhesive compound and, second, at least one second sealing compound are arranged circumferentially, at least on part of the length of the frame, wherein the two sealing and/or adhesive compounds differ with regard to their curing time and/or gas permeability.
Claim 57 claims a method for producing a photovoltaic concentrator module according to any of the preceding claims, which is characterized by the following features.
Namely, that a frame connecting a lens plate and a baseplate is arranged along the edge of the lens plate and the baseplate, and that between the frame and the lens plate and/or the frame and the baseplate, first, at least one first sealing compound and/or adhesive compound and, second, at least one second sealing compound are introduced circumferentially along the frame over at least part of its length, wherein the two sealing and/or adhesive compounds differ with regard to their curing times and/or gas permeabilities. Although mention is made here of a first sealing compound and/or adhesive compound and a second sealing compound, the fact that one of the adhesive compounds serves only for fixing a plate during the production process by means of UV light, while another adhesive compound having a long service life is used for main sealing, cannot be inferred here.